Shrinkwrap is not playing nice with neck bone.

.blend file:

It’s quite hard to explain, so here is a video.

The eyeball is controlled by an armature and then shrinkwrapped onto an icosphere.

Can anyone help with this?

The video is not showing up. Error message.

Edit: Ok, should be working now. I accidentally deleted an underscore from the video ID.
Goddamnit, I thought it was just a temporary issue when uploading. ._.